Intelligent orthosis

ABSTRACT

An orthotic frame has proximal and distal frame members joined by a knee joint, and a foot support joined by an ankle joint to a distal end of the distal frame. A knee actuator connected between the proximal and distal frame members has a selective stiffness allowing selection of a relatively rigid stiffness during stance and a relatively flexible stiffness during swing. The stiffness of the knee actuator is selected according to the gait cycle, either mechanically according to dorsal flexion of the ankle joint or electronically according to gait cycle phases recognized based on read sensor data. An ambulatory unit gathers data from sensors located on the orthotic frame. Sensor data may be provided to a base unit for diagnostic and biomechanical evaluation, or evaluated by the ambulatory unit to control active components of the orthotic frame according to the recognized gait cycle phases for functional compensation.

CROSS REFERENCE TO RELATED APPLICATION DATA

This application is a continuation of U.S. application Ser. No.11/819,543 filed Jun. 28, 2007 which claims the benefit of U.S.Provisional Application No. 60/817,347 filed Jun. 30, 2006.

FIELD OF THE INVENTION

The present invention relates an orthotic brace, and more particularlyto an intelligent knee, ankle, and foot orthosis for biomechanicalevaluation and functional compensation of joint disorders.

BACKGROUND

Patients with partial or complete paralysis or muscular weakness of theextremities often are assisted in mobility by the use of an orthoticdevice or orthosis. For example, a patient with weakness of leg musclesmay employ an orthosis to provide assistance in supporting body weightduring the stance phase of the gait cycle.

A knee, ankle, and foot orthosis (KAFO) typically extends from thepatient's upper leg to the lower leg, and provides a foot support. Inorder to accommodate normal flexion of the patient's knee, a knee jointor hinge joins an upper portion of the KAFO (which is worn attached tothe patient's upper leg) to a lower portion of the KAFO (which is wornattached to the patient's lower leg). Additionally, an ankle joint maybe provided between the lower portion and the foot support to allow, orcontrol, flexion of the foot.

One common aspect of a knee orthotic, including a KAFO, is the abilityto lock the knee joint or, hinge in a straight legged position so thatthe rigidly locked KAFO supports the patient in stance in compensationfor weakness or paralysis of the leg muscles.

Various devices have been devised for locking the knee hinge or joint ofan orthosis such as a KAFO. However, while it is advantageous to lockthe knee for support during stance, it is problematic for the knee toremain locked during the swing phase of the gait cycle.

With an orthotic knee continuously locked, a patient must perform anunnatural and inefficient motion to affect a walking gait, by liftingthe leg with the orthosis to provide for clearance of the foot from theground as the leg swings forward.

Further, in the case of a KAFO, it is more likely that the patientwearing the KAFO suffers from a weakness or abnormality in musclesrelated to dorsal or plantar flexion of the foot. A patient who has, forexample, weakened dorsal flexors of the foot may lack the ability forproper dorsal flexion of the foot during the gait cycle, in addition tolacking leg strength for support. As a result, gait problems resultingfrom a rigidly locked orthotic knee may be exacerbated by an inabilityof the patient to dorsally flex the foot and thereby raise the toes toavoid toe drag during the swing phase of the gait.

In addition to the leg lift required for clearance in the leg with alocked knee, further lifting may be required for clearance of the toesor forefoot. Not only does a her awkwardness or inefficiency of the gaitresult, a safety consideration arises in the increased risk of fall dueto toe drag if sufficient clearance is not consistently achieved.

It is therefore desirable for an orthotic knee joint to be selectivelylockable, so that support may be provided during the stance phase whileknee flexion is allowed during the swing phase to facilitate a morenormal, and more efficient, gait. Further, in the case of a KAFO, it isdesirable for ankle and knee compensation strategies to be coordinatedin function so that the patient's gait is additionally improved.

In addition to gait problems that result from a continuously lockedknee, a knee that is rigidly locked does not provide shock absorptionthat may be achieved by even a small degree of flexion of the knee.

SUMMARY

The present invention relates to an intelligent knee, ankle, and footorthosis (KAFO). The KAFO incorporates both passive and activecomponents in an orthotic frame to compensate for muscle weakness duringwalking, standing, and other activities, to support a user and to assistthe user in approximating or achieving a normal gait.

The KAFO acts simultaneously on knee and ankle joints to apply activecompensation strategies to provide an integral solution to mobilityproblems related to weakness of leg muscles, and particularly quadricepsweakness.

The KAFO may provide various compensation strategies, includingassistance in supporting the patient during loading of the leg (duringthe stance phase), free or controlled flexion of the knee joint duringthe swing phase, assistance in push off prior to the swing phase,control of ankle flexion to avoid toe drag or drop foot, and assistancein extension of the knee at the end of the swing phase.

The KAFO comprises a mechanical orthotic frame that has a proximal(thigh) frame portion joined by a knee joint to a distal (shank) frameportion. A foot support is joined to the distal frame portion by anankle joint.

A patient wears the orthotic frame with the proximal frame portionfitted to a leg above the knee and the distal frame portion fitted tothe leg below the knee, and with the knee joint aligned with thepatient's knee. The patient's foot is supported on the foot support, andthe ankle joint is aligned with the patient's ankle.

A knee actuator is provided to control flexion of the knee joint. Incertain embodiments, the knee actuator is a passive or semi-passivedevice that provides a fixed, selectable, or variable resistance to theflexion of the knee joint. Such a knee actuator restricts the flexion ofthe knee joint during the stance phase (after heel strike) to providesupport of the patient, and allows relatively free flexion of the kneejoint during the swing phase.

In other embodiments, the knee actuator is an active device that appliesa torque to the knee joint to cause a desired flexion of the orthoticframe at the knee joint.

An ankle actuator provides control of dorsal and plantar flexion of theankle joint, assisting in the correction of problems such as foot slapgait, toe drop, and other problems related to weakness in dorsal orplantar flexors of the foot. As with the knee actuator, both passive andactive devices may be employed.

The KAFO is instrumented with a multiple purpose sensor set, whichenables measurement of physical variables related to comfort (pressureand strain), kinematics (sagittal plane angles of the knee and anklejoints, rotational velocities of the shank and foot segments, and footaccelerations, for example), and knee joint and actuator status.

Information gathered by the sensor set is used for monitoring purposesand for control of active components of the KAFO. The gatheredinformation may be employed to determine or recognize certain aspects orphases of the gait cycle, and to drive active components of themechanical orthotic frame to provide assistance at relevant times duringthe gait cycle. For example, active actuators may help in assisting apatient with muscular weaknesses, such as a patient with weakquadriceps, in regaining functionality.

This intelligent system comprises multiple sensors, such as pressuresensors, strain gauges, angular, sensors, angular velocity sensors, andground reaction force sensors. Other sensor types may also be included.The information from these sensors is gathered in, and evaluated by, acontrol unit that in turn controls a set of actuators that activate theKAFO to assist the user. The control function is based on recognizingphases of the gait cycle and responding to strategic needs in the gaitcycle to assist the user to maintain “normal” gait cycle.

The sensors and actuators are strategically placed about or near theknee joint, the ankle joint, or at other relevant locations of themechanical orthotic to provide the relevant information and perform therequired assistance during gait.

Also, information gathered is useful during fitting and adjustment ofthe KAFO. The KAFO allows monitoring of various parameters that providea basis for tracking activities of the user, which can be helpful inassessment and follow-up of the user.

These and other features, aspects, and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims, and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an intelligent knee, ankle, and footorthotic (IKAFO) according to one embodiment of the present invention.

FIG. 2 is a perspective view of an orthotic frame of the IKAFO shown inFIG. 1.

FIG. 3 is a perspective view of a pelotte carrier of the IKAFO shown inFIG. 1.

FIG. 4 is a perspective view of a knee joint according to one embodimentof the present invention.

FIG. 5A is an exploded view of a knee actuator according to oneembodiment of the present invention.

FIG. 5B is a schematic representation of a damped knee actuator.

FIG. 6 is a perspective view of the knee actuator of FIG. 4 partiallyassembled.

FIG. 7 is an exploded perspective view of an ankle actuator according toone embodiment of the present invention.

FIG. 8 is a block diagram identifying instrumentation applied to theorthotic frame in one embodiment of the present invention.

FIG. 9 is a block diagram of an ambulatory control unit for a KAFOaccording to an embodiment of the present invention.

FIG. 10 is a state transition diagram depicting transitions betweenactivity states.

FIG. 11A is a graph depicting measured sensor data during an activity ofsitting down from a standing position.

FIG. 11B is a graph depicting measured sensor, data during an activityof standing up from a seated position.

FIG. 12A is a graph depicting measured sensor data during an activity ofbeginning to walk (transitioning from standing stable to walking).

FIG. 12B is a graph depicting measured sensor data during an activity ofstopping walking (transitioning from walking to standing stable).

FIG. 13A is a graph depicting measured sensor data during a walking upstairs activity.

FIG. 13B is a graph depicting measured sensor data during a walking downstairs activity.

FIG. 14A is a graph depicting measured sensor data during an upslopewalking activity.

FIG. 14B is a graph depicting measured sensor data during a down slopewalking activity.

FIG. 15A is a graph depicting measured sensor data during a walkingactivity, showing data for four walking gait cycles according to anormal gait.

FIG. 15B is a graph depicting measured sensor data during a walkingactivity, showing data for four walking gait cycles according to asimulated abnormal or pathological, and gait.

FIG. 16A is a graph depicting measured sensor data during a walkingactivity and a calculated activity recognition result based on arecognition rule applied to the measured data, in a normal walking gait.

FIG. 16B is a graph depicting measured sensor data during a walkingactivity and a calculated activity recognition result based on arecognition rule applied to the measured data, in a simulated abnormal(pathological) walking gait.

Similar reference characters denote corresponding features consistentlythroughout the attached drawings.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

The present invention is an intelligent knee, ankle, and foot orthosis(IKAFO) for biomechanical evaluation and functional compensation ofjoint disorders. Referring to FIG. 1, an embodiment of an IKAFO isillustrated, designated generally as 10 in the figures. The IKAFOassists a patient suffering from muscular weakness or other problemsaffecting the patient's gait by providing support and compensation fordiminished muscular function or weakness.

The IKAFO 10 shown in FIG. 1 comprises an orthotic frame 100 having anupper or proximal frame 110 and a lower or distal frame 120 joined by amechanical knee joint 200. A foot support 130 is joined to a distal endof the distal frame 120 by an ankle joint 140.

The orthotic frame 100 is configured to be worn by a user or patient byfitting the upper frame 110 to the upper leg, above the knee, andfitting the lower frame 120 to the lower leg, below the knee, with theknee joint 200 pivotally aligned with the patient's knee. Thus, supportis provided to a patient by the orthotic frame 100, while the knee andankle joints 200, 140 of the orthotic frame 100 allow controlled flexionof the patient's knee and ankle.

Control of the knee and ankle joints 200, 140 by actuators installed on,and working in conjunction with, the orthotic frame 100 allows theorthotic frame 100 to support a patient's weight during certainactivities, while also allowing flexion during other activities. Variousambulatory and related activities performed by a person place differentrequirements on the function of the IKAFO.

For example, while a patient is standing stably, the IKAFO may berequired to support the patient's weight, suggesting that the knee joint200 must be locked or subjected to a high torque so that the orthoticframe 100, and therefore the patient's leg remains extended. Conversely,the knee joint 200 must clearly be allowed to flex freely if the patientdesires to sit down comfortably.

Similarly, while a patient is walking, different phases of the walkinggait place different requirements on the IKAFO. During a stance phase ofthe walking gait, for example, the patient's weight is supported by theleg in contact with the ground. As with standing stably, the patient'sweight must be supported and a knee joint 200 that is locked orsubjected to a high torque contributes to such support. On the otherhand, during the swing phase of the gait, it is desirable that the kneejoint 200 is allowed to swing freely, or to swing subject to a suitabletorque that the knee joint 200 is flexed so that the patient's footclears the floor. Similar considerations may be recognized with respectto the ankle joint, wherein plantar and dorsal flexion of the may becontrolled differently, or subject to different requirements, duringdifferent gait phases.

The upper and lower frames 110, 120 of the orthotic frame 100 are fittedto the user's leg with pelotte carriers 150 which are fastened to theuser's leg with straps 152 that may be tightened to an appropriate fit.

The upper and lower frames 110, 120 are preferably adjustable in length,to accommodate fitting to patients of different sizes and physicalneeds. Referring to FIG. 2, the upper and lower frames 110, 120 are eachcomprised of a side bar or strut 116 that is adjustable in length. Eachside bar 112 in the illustrated embodiment comprises an upper and alower member 114, 116 slidably engaged to one another. Clamping orlocking means are provided in the form of a clamp, bolt, or otherfastener to lock the upper and lower members 114, 116 together at adesired length.

While the illustrated embodiment employs a single side bar or strut 116in each of the upper and lower frames 110, 120, alternative embodimentsmay employ additional side bars or struts, such as a side bar or struton each side of the patient's leg, a bar or strut located at the frontor rear of the leg, or other configurations.

Pelotte carriers 150 are fixed to the upper and lower members 114, 116respectively, such that the distance between the pelotte carriers 150 isvaried according to the length of the side bar 112.

The illustrated orthotic frame 100 is of a lateral side barconfiguration, with the pelotte carriers 150 fastened along the sidebars 112. Referring to FIG. 3, the pelotte carriers 150 are in the formof rigid semi-circular or U shaped members configured to be positionedabout the front of a patient's leg and secured to the leg by straps 152extending and secured about the rear of the patient's leg to fasten theorthotic frame 100 in position.

Padding material or cushions 154 are disposed along an inner surface 156of each of the pelotte carriers 150 to provide for patient comfort aswell as fitting. The padding material or cushions 154 may be removablesuch that proper fitting of the orthotic frame 100 to the patient's legmay be accomplished by fitting a padding material or cushions 154 of anappropriate thickness. Also, the pelotte carriers 150 may be sized forcorrect patient fit, or bent to accommodate a slightly larger or smallerleg.

The knee joint 200 connects the upper and lower frames 110, 120.Numerous types of orthotic knee joints and hinges are known, includingsingle axis joints, polycentric joints, and others. A single axis jointfunctions essentially as a simple hinge, allowing for pivoting motion ofthe upper and lower frames 110, 120 relative to each other about asingle, fixed axis of rotation. Polycentric joints incorporateadditional rotational axes to allow for a more complex pivoting motionbetween the upper and lower frames 110, 120. In certain embodiments of apolycentric joint, elements of the joint may be geared or otherwiseinterconnected so that rotational motion about the various axes iscoordinated.

While any type of knee joint or hinge or other rotary element may beused in the IKAFO, it is preferred to employ an orthotic knee joint thataccurately models the movement of a human knee about the instant helicalaxis of the physiological knee.

In one preferred embodiment, the knee joint 200 is a four-point kneejoint such as one illustrated in FIG. 4 and described in Spanish PatentApplication No. 200302322, incorporated herein by reference in itsentirely.

The four-point knee joint comprises a fixed lower reference 202reproducing the physiological curvature of the knee, and an upperfollower 204 movably in contact with the lower reference 202. Two levers206 connect and transmit forces between the lower reference 202 and theupper follower 204. The levers 206 are arranged to guide the movement ofthe lower reference 202 and the upper follower 204 to reproduce movementaccording to the physiological curvature of the knee, thereby mimickingflexion of the knee about a variable instantaneous axis of rotation(instantaneous helical axis) of the knee.

The four-point knee joint reduces variations between the movement of thepatient's leg and movement of the orthotic frame 100. Accordingly,improvements in patient comfort and gait efficiency are realized.

Patient comfort is improved because reduced variation between thepatient and the orthotic frame 100 in movement results in decreasedabrasion, or pressure, against the patient by interfaces with theorthotic frame 100, and in a reduction in the necessity for excessivelytight attachment of the orthotic frame 100 to the patient.

Gait efficiencies are realized because patient energy expenditures ormovements related to compensation for relative movement of the orthoticframe 100 are reduced or eliminated.

Additionally, damage to internal tissues such as ligaments, cartilage,and tendons of the knee joint, is reduced or eliminated because stressesto these tissues caused by the differences in motion of the patientsknee joint and the orthotic knee joint are reduced or eliminated.

A knee actuator 300 is disposed on the orthotic frame 100 to controlflexion of the knee joint 200, and an ankle actuator 400 is disposed onthe orthotic frame 100 to control flexion of the ankle joint 140. Theknee actuator controls flexion of the knee joint 200 by providing avariable resistive force against movement of the knee joint 200.

In certain embodiments, the knee actuator 300 is a passive orsemi-passive device that provides a fixed, selectable, or variableresistance to the flexion of the knee joint 200. Such a knee actuator300 may, for example, restrict the flexion of the knee joint 200 duringthe stance phase (after heel strike) to provide support of the patient,and allow relatively free flexion of the knee joint 200 during the swingphase.

In other embodiments, the knee actuator 300 may be an active device thatapplies a torque to orthotic frame 100 about the knee joint 200 to causea desired flexion of the orthotic frame 100 at the knee joint 200.

In the illustrated embodiment, a semi-passive knee joint 300 isemployed. The knee joint 300 is referred to as semi-passive since it isnot a source of a moving force of the orthotic frame 100 or the kneejoint 200, but is adaptable to provide a varied resistance to themovement of the knee joint 200. In other embodiments, an active kneejoint may be employed to provide a moving force to the orthotic frame toflex and/or extend the knee joint, compensating further for a patient'smuscular weakness, restricted movement, or the like.

The illustrated embodiment employs a single knee actuator 300 providedin the form of a compressible strut extended between the proximal frame110 and the distal frame 120. The knee actuator 300 is configured tobias the proximal 110 and distal frames 120 of the orthotic frame 100into an extended or straight legged position. Alternate configurationsmay be employed for a knee actuator, such as a pair of compressiblestrut-type actuators disposed on opposite sides of the orthotic frame100, or alternate types of knee actuator devices incorporated to providedesired torque, bias, or other forces applied to move or influencemotion of the orthotic frame 100 components about the knee joint 200.

It is desirable, according to the illustrated embodiment, for the kneeactuator 300 to be relatively stiff in compression during the stancephase of the gait cycle, or during certain activities wherein apatient's weight is to be supported by the orthotic frame 100, so thatthe patient is adequately supported by the orthotic frame 100. On theother hand, it is desirable for the knee actuator 300 to be relativelysoft in compression during the swing phase of the gait cycle, or duringactivities wherein knee flexion is desirable, allowing the patient tobend and extend the knee naturally.

Accordingly, the knee actuator 300 has a selective stiffness or flexion,allowing selection of either of a first compressible stiffness and asecond compressible stiffness, so that the knee actuator 300 may providea relatively rigid compressible stiffness during stance and a relativelyflexible compressible stiffness during swing. The knee actuator 300 isprovided with a selector 330 that is operable for selecting therelatively rigid or the relatively flexible stiffness.

One example of a knee actuator 300 having a selective compressiblestiffness is illustrated in FIGS. 5 and 6. According to the illustratedembodiment, the knee actuator 300 comprises a first cylinder 310, and asecond cylinder 320 slidably disposed within a first end 312 of thefirst cylinder 310. A first spring 302 is disposed within the firstcylinder 310 to bias the first cylinder 310 toward an extended position.

A shaft 304 is slidably disposed within the second cylinder 320. Asecond spring 306 is disposed within the second cylinder 320 to bias theshaft 304 toward an extended position.

It can be recognized that movement of the second cylinder 320 into thefirst cylinder 310 compresses the first spring 302, while movement ofthe shaft 304 into second cylinder compresses the second spring 306,thereby providing a first and second compressive stiffness.

While the illustrated knee actuator 300 employs a pair of springs toachieve a selectable compressive stiffness, alternate configurations maybe employed such as one or more springs having a variable stiffness, oneor more springs supplemented with other means, such as a brake or clutchor other element to selectively lock or damp or otherwise limit themovement of the knee joint 200. Further, spring elements may be replacedwith other resilient or compressible members such as hydraulic,pneumatic, or other actuators using a compressible or incompressiblefluid, electrical actuators, elements formed from a resilient orcompressible material, or the like. The knee actuator may includepassive or active components, or a combination thereof.

Additionally, instead of a linear configuration such as the illustratedknee actuator 300, a knee actuator may be configured to employ rotaryelements which may be incorporated within a knee joint or elsewhere onthe orthotic frame 100.

The knee actuator 300 may be further altered to provide additionalselectable compressive stiffness settings, or may be configured suchthat a continuously variable compressive stiffness is provided. Suchadditional selectable compressive stiffness settings may be achieved byproviding additional cylinder and spring combinations in the mannerillustrated, or otherwise according to the above discussed alternatives.

The knee actuator 300 may also be provided with one or more dampingelement, such as a damper 341 as shown in FIG. 5B.

As configured in FIG. 1, a connecting member 305 of the shaft 304 isattached to a mounting support 118 on the upper frame 110, and aconnecting member 314 of the first cylinder 310 is attached to amounting support 128 on the lower frame 120.

The first spring 302 is a relatively soft spring, while the secondspring 306 is relatively stiff. Thus, by selectively enabling the first302 or the second 306 spring, the knee actuator 300 provides arelatively soft or a relatively stiff compression, respectively.

The selector 330 is in the form of a locking mechanism provided toselectively activate or enable the first spring 302. The lockingmechanism comprises a locking collar 334 located, in one embodiment, atthe first end 312 of the first cylinder, and disposed about the secondcylinder 320.

One or more longitudinal tracks 322 are formed on the surface of thesecond cylinder 320. The tracks 322 each accommodate a ball 336 whichcan move freely along the track 322. A locking detent 324 is providedalongside each track 322, and the locking detents 324 are each locatedat a same distance from the end of the second cylinder 320.

The balls 336 are retained within the tracks 322 by the locking collar334, and the balls are movable by the locking collar 334 into thelocking detents 324 when the second cylinder 320 is positioned such thatthe balls 336 within the locking collar 334 are aligned with the lockingdetents 324.

When the balls 336 are moved into the locking detents 324 by the lockingcollar 334, the second cylinder 320 is prevented from movement relativeto the first cylinder 310. Accordingly, when the second cylinder 320 islocked in place by the locking mechanism, the knee actuator 300 iscompressible according to the relatively stiff second spring 306.Conversely, when the second cylinder 320 is unlocked, the knee actuator300 is compressible according to the relatively soft first spring 302.

Thus, moving the locking collar 334 allows selection of either of arelatively flexible mode (according to the first spring 302) and arelatively stiff mode (according to the second spring 306).

The locking collar 334 may be provided with a torsion spring 338 to biasthe locking collar 334 toward its locking position, such that the secondcylinder 320 will become automatically locked in position when thelocking detents 324 become aligned with the balls 336 of the lockingcollar 334.

According to one configuration, the locking detents 324 are positionedsuch that the locking position of the second cylinder 320 is at or nearthe maximum extension of the second cylinder 320 from the first cylinder310.

When the knee actuator 300 of this configuration is disposed between thelower 120 and upper 110 frames of the orthotic frame 100, the lockingposition of the knee actuator 300 corresponds to the maximum extension,or straight legged position, of the orthotic frame 100.

Accordingly, locking the knee actuator 300 when the orthotic frame 100is in the straight legged position causes flexion of the knee joint 200to be subject to the relatively stiff second spring 306, limitingflexion of the knee joint 200 and providing support for the patient.

While the knee actuator 300 is locked, the knee joint 200 itself is notlocked, but is instead movable subject to the relatively stiff secondspring 306 of the knee actuator 300. Therefore, shock absorption isprovided during the stance phase of the gait by flexion that ispermitted by the second spring 306.

It is desirable for the knee actuator 300 to be locked, or in a stancestate, to provide the limited flexion of the relatively stiff secondspring 306 during the stance phase of the gait cycle so that the patientis adequately supported in stance by the orthotic frame 100. Similarly,it is desirable for the knee actuator 300 to be unlocked, or in a swingstate, during the swing phase of the gait cycle, so that the knee joint200 of the orthotic frame 100 may be flexed subject to the relativelysoft first spring 302, allowing knee bend and extension of a naturalgait during the swing phase.

It is desirable for the selector 330 to produce an audible sound, suchas a clicking sound, when the selector 330 is moved into at least one ofthe locked and unlocked positions, to provide an audible feedback to theuser. For example, if the selector 330 is configured to produce a clickwhen the knee actuator 300 is locked, the user may rely on the click asa signal that the knee actuator 300 is locked and the IKAFO 10 willsupport the user. Conversely, if no sound is heard, the user recognizesan “unsafe” condition and may take a remedial action such as relying oncrutches, a cane, or the like for support.

A control element is connected to the selector of the knee actuator 300,and is configured to move the selector 330 between the first and secondposition according to at least one aspect of a walking gait cycle, orone aspect of an ambulatory or related activity. For example, it isdesirable for the relatively stiff second spring 306 of the kneeactuator 300 to be selected during the stance phase of the patient'swalking gait, so that the patient is supported by the orthotic frame.Similarly, it is desirable for the relatively flexible first spring 302of the knee actuator to be selected during the swing phase of thepatient's gait so that the leg may swing forward with the knee bent inthe manner of a normal, natural gait.

In one embodiment, the control element allows selection of the stiffnessof the knee actuator 300 according to the angle of flexion of the ankle.Because the angle of flexion of the ankle (and thus of the ankle joint140) varies generally predictably during the course of a normal walkinggait, the angle of flexion of the ankle may be used to determine, atleast roughly, certain phases or points during the gait.

In a simplified approach, when the ankle reaches a predeterminedposition of dorsal flexion, the selector 330 of the knee actuator 300 isactivated to select the relatively flexible first spring 302, making itpossible for the patient to bend the knee. Subsequently, when the kneeis extended later in the gait cycle (and the knee actuator 300 reachesits extended position), and when the ankle has returned to a lessdorsally flexed position, the knee actuator 300 is locked leaving therelatively stiff second spring 306 active.

For example, it can be recognized that the ankle typically reaches amaximum degree of dorsiflexion just prior to toe-off, indicating the endof the stance phase. Accordingly, this may provide a cue to release theknee joint 200 by selecting the relatively flexible compressiblestiffness of the knee actuator 300. Moving the selector 330 according tothe ankle dorsiflexion allows setting the knee actuator 300 accordinglyso that the knee joint 200 is free to flex during the swing phase.

Conversely, as the ankle plantarflexes somewhat during the swing phase,the selector 330 may be moved accordingly such that when the leg reachesfull extension at the end of the swing phase, the knee actuator 300 willbe locked, providing the support of the relatively stiff compressiblestiffness of the knee actuator 300 during the subsequent stance phase.

This simplified approach to selecting the stiffness of the knee actuator300 may be accomplished by an entirely mechanical arrangement, whereinthe control element comprises a cable 340 or cable pushrod or the likeconnected between the ankle or the foot plate and the selector 330 ofthe knee actuator 300. The cable 340 is movable according to the angleof the ankle, so that when the ankle or foot plate reaches a certaindegree of dorsal flexion, the cable 340 operates the selector 330 tounlock the knee actuator 300 and activate the flexible setting of theknee actuator 300.

Since the ankle is biased toward a neutral position (in neither dorsalnor plantar flexion), it follows that the dorsal flexion of the ankledecreases after toe-off and during the swing phase. Thus, the selector330 is returned into the position for activating the stiff setting ofthe knee actuator so that when the leg is straightened at the end of theswing phase the stiff setting of the knee actuator is activated.

Typically, the cable will be adjusted to activate the flexible settingof the knee actuator 300 when the dorsal flexion of the ankle is at, orapproaching, a maximum toward the end of the stance phase of the gaitcycle (just before toe-off). With the flexible setting of the kneeactuator 300 activated, the patient's knee is allowed to flex under thepatient's weight at the end of the stance phase, as the patient's otherleg approaches heal strike and the beginning of the stance phase tosupport the patient.

The cable may be adjusted differently to suit different patient needs,or different gait issues.

In an electro-mechanical approach to changing the biasing force of theknee actuator 300, a control element comprises a solenoid 342 to operatethe selector 330 according to an electronic control signal. The solenoid342 is driven by an electronic control signal which may be generatedfrom an electronic measurement of the flexion of the ankle or from otherinformation.

The control signal may be derived simply from measurement of the dorsalflexion of the ankle, functioning similarly to the mechanical approachexcept replacing the function of cable 340 the solenoid 342, a sensorfor measuring the ankle flexion, and an electronic circuit to interpretthe sensor and generate the control signal.

Alternatively, the control signal may be derived from informationderived from additional sensors disposed on the orthotic frame 100, aswell as tuning factors provided during a fitting or adjustment processto more precisely identify a correct position during the gait cycle toreduce the knee stiffness. The control signal may also be derived from auser switch or control 880 that allows the user to override automatedgeneration of the signal, for example to continuously lock the kneeactuator 300 during a stair climbing or descending activity.

An ankle actuator 400 is disposed on the orthotic frame 100 to controlflexion of the ankle joint 140, and to provide assistance orcompensation for muscular function related to dorsal and plantar flexionof the foot. The ankle actuator 400 allows partial storage of elasticenergy during dorsal flexion of the foot and recovery of the storedenergy during plantar flexion of the foot to avoid drop foot.

In an embodiment of FIG. 7, an ankle actuator 400 comprises a singleshaft 410. A stopping member 416 is disposed on the shaft 410 proximateto a coupling fitting 414 at a first end 412 of the shaft 410 and asliding member 402 is slidably disposed on the shaft 410.

A first spring 404 is disposed on the shaft 410 between the stoppingmember 416 and the sliding member 402, and a second spring 406 isdisposed on the shaft 410 on the side of the stopping member 416 of asecond end 418 of the shaft 410.

The shaft 410 is movably contained in a cylindrical housing 420 with thefirst end 412 of the shaft 410 extending from a first end 422 of thehousing, and the stopping member 416 is fixed to the housing 420. In theillustrated embodiment, the cylindrical housing 420 comprises a firsthousing half 424 and a second housing half 426 which are coupled toopposite sides of the sliding member 402 of the shaft 410.

Referring to FIG. 1, the ankle actuator 400 is shown coupled between thelower frame 120 and the foot support 130, with the coupling fitting 414attached to a mounting support 129 on the lower frame 120 and a couplingfitting 419 of the cylindrical housing 420 attached to a mountingsupport 132 on the foot support 130 or a lower member of the ankle joint140.

It can be seen that the ankle actuator 400 provides different torques tothe ankle joint 140 according to the selection of the first 404 andsecond 406 springs, so that the ankle actuator 400 may be configured forassistance or compensation in either, or both, of dorsal and plantarflexion of the foot.

As discussed above with respect to the knee actuator 300, the ankleactuator 400 may be alternatively embodied. Various passive or activeconfigurations may employ rotary or linear elements, includinghydraulic, pneumatic, or other actuators using a compressible orincompressible fluid, electrical actuators, and elements formed from aresilient or compressible material, or the like. The ankle actuator mayinclude passive or active components, or a combination thereof.

Referring to FIG. 8, the IKAFO is instrumented with a multiple purposesensor set 800, which enables measurement of physical variables relatedto comfort (pressure and strain), kinematics (sagittal plane angles ofthe knee and ankle joints, rotational velocities of the shank and footsegments, and foot accelerations, for example), knee joint and actuatorstatus, and other events related to ambulatory and related activities,including aspects of the gait cycle such as initial foot contact, footflat, heel off, and toe off.

Data gathered from the sensor set 800 may be analyzed for biomechanicalevaluation of the patient's use of the IKAFO, which may be useful forfitting of the IKAFO as well as monitoring the patient's progress anddiagnosing problems with the patient relating to the IKAFO.

Further, real-time analysis of the data from the sensor set 800 allowsidentification of ambulatory and related activities that are performedby the patient, and can contribute to functional compensation providedby the IKAFO. For example, while control of the knee actuator 300 wasdescribed above with respect to ankle flexion, it can be recognized thata broader range of compensation strategies may be employed based onrecognition of different activities such as sitting down, standing up,walking up or down stairs or a slope, or other activities that may placedifferent requirements on the functionality of the IKAFO.

The sensor set may include pressure sensors 810, strain gauges 820, aknee angle sensor 830, a knee status sensor 840, an ankle angle sensor850, inertial measurement units (IMUs) 860, and foot contact sensors870. An ambulatory data processing unit (ambulatory unit) 900 isco-located with the IKAFO (mounted to the orthotic frame 100 or carriedby the patient, for example), to monitor the sensors and to processsensor data to control actuators of the IKAFO. The ambulatory unit 900also provides data communication to a base unit 1000 where furtheranalysis of the sensor data may be performed.

Pressure sensors 810 are disposed on portions of the orthotic frame 100that interface directly with a patient. Pressure sensors 810 may belocated on the pelotte carriers 150, such as between the pelotte carrier150 and a padding material or cushion 154. In one embodiment, thepressure sensors 810 are strain gages, located on the lateral aspect ofeach pelotte carrier 150 and protected against mechanical interactionsand environmental factors.

Additionally, strain gauges 820 may be disposed on the orthotic frame100 to measure stresses on the components of the orthotic frame 100 thatare related to various ambulatory activities. Strain gauges are appliedto the side bars 112 of the upper and lower frames 110, 120 to measuredeformation of the side bars 112 that are related to loading of the sidebars 112 during various ambulatory activities, to provide a measurementof the loading.

A knee joint angle sensor 830 is disposed on or proximate to the kneejoint 200, and is configured to measure the knee angle (an angle betweenthe proximate and distal frame portions). In one embodiment, the kneejoint angle sensor 830 is a precision potentiometer mounted on attachingmembers of the knee joint 200 to measure the angle in one axis of theknee hinge.

An actuator lock mechanism sensor 840 is a sensor disposed on orproximate to the knee actuator 300 to sense the lock/unlock status ofthe actuator lock mechanism. In one embodiment, the actuator lockmechanism sensor 840 is a contact switch disposed to determine thelock/unlock status of the actuator lock mechanism based on the positionof the actuator lock mechanism.

The actuator lock mechanism sensor 840 is useful, in addition to simplygathering information for biomechanical evaluation of the IKAFO or thepatient, to provide an audible or other signal or warning relating tothe lock status of the knee actuator 300. For example, a signal may begenerated to indicate to the patient that the knee actuator 300 has beenlocked, so that the patient can confidently rely on the IKAFO to supporther weight. Similarly, an alarm may be generated if a control signal hasbeen sent to lock the knee actuator 300, but the locking mechanism isnot properly activated.

Inertial measurement units (IMUs) are provided on the shank (lower frame120) and foot parts of the orthotic frame 100. A foot IMU 860 ispositioned below the ankle joint and a shank IMU 860 is located alongthe lower (or shank) frame portion 120. The foot IMU 860 may becontained within a housing or small box disposed below the ankle joint,and the shank IMU 860 may be collocated with other electronics orinterconnections in a junction or interconnection box located along theshank (distal) frame portion. Each of the IMUs 860 comprises a rategyroscope and a biaxial accelerometer.

In addition, or alternatively to the IMUs (and other sensors), one ormore linear accelerometers may be employed to sense movement orkinematic information of any of the moving parts of the orthotic frame100. It can be recognized that such linear accelerometers may beemployed to provide movement or kinematic information that isunavailable from, or that is redundant to, other sensors.

Foot contact sensors 870 are provided on the foot plate 130 in the formof pressure sensors or contact switches to detect foot contact with theground. Foot contact sensors 870 are located at both front and rearparts of the foot plate 130, to detect both toe (or fore foot) and heel(or rear foot) contact events. The foot contact sensors 870 may bedisposed between the foot plate 130 and a soft insole.

Alternative to foot contact sensors 870 provided on the foot plate 130,pressure or contact or other types of sensors may be deployed elsewhereon the orthotic frame 100 to sense foot contact status such as footstrike or lift or related events. For example, accelerometers may detectmotion or impact associated with foot strike or lift events, and straingauges positioned variously about the orthotic frame may provideinformation relating to the loading of the orthotic frame that may beassociated with foot strike and lift events.

Other types of sensors may be used in addition to, or in place of, thosedescribed. For example, Global Positioning System (GPS), magnetic flux,or other types of sensors may be employed to provide movement orkinematic information that is unavailable from, or that is redundant to,other sensors.

The ambulatory unit 900 gathers kinematic information from the varioussensors disposed on the orthotic frame 100. The kinematic informationmay be processed locally by the ambulatory unit 900, and may be used tocontrol actuators (such as the knee actuator 300) of the IKAFO inresponse to events or conditions that are detected or recognized by theambulatory unit 900 based on analysis of the kinematic data. Theambulatory unit 900 also provides an interface for forwarding gathereddata to the base unit 1000 for further processing and analysis.

Referring to FIG. 9, the ambulatory unit 900 comprises generallyconventional control hardware architecture. Such a control hardwarearchitecture typically comprises a microprocessor 910 connected by a bus990 to an area of main memory 920, comprising both read only memory(ROM) 922, and random access memory (RAM) 924.

The microprocessor 910 may be in communication, via bus 990, with astorage device 930 such as a disk storage device or a removable mediamemory device such as a removable memory card or the like. Input/outputdevices 940, 950 are included to provide an interface to the sensors andactuators of the IKAFO 10.

A communication interface 960 is provided for communication between theambulatory unit 900 and the base unit 1000. The communication interface960 may be a wireless interface, employing an RF, infra-red (IR), orother wireless communication medium. Alternatively, the communicationinterface 960 may be wired, using a cable in connection with the baseunit 1000.

A control program may be stored in the ROM 922, or loaded into memory920 from storage device 930, for execution by the microprocessor. Thecontrol program functions to read sensor data from the sensor inputs,and to evaluate the sensor data for control of actuators of the orthoticframe 100. The control program also may store the sensor data in thestorage device 930 for later recall and transmission to the base unit1000, or transmit the sensor data to the base unit 1000 in real time.

The control program thus reads sensor data for both real-time control ofthe IKAFO 10 and for later analysis in the base unit 1000. Sensor datasampling rates for real-time functions are typically higher thansampling rates for later analysis. For example, a sampling rate of 100Hz may be employed for real-time control functions, while a samplingrate of 30 Hz may be employed for data that is merely to be stored forlater analysis at the base unit. For data storage, it can be recognizedthat data rate and the capacity of the storage device 930 influence theamount of information that may be recorded for later analysis.

In the electro-mechanical approach to changing the biasing force of theknee actuator 300, a control program executed by the ambulatory unit 900determines when to signal the knee selector 330 to select the rigidsetting or the flexible setting. While a simple control program may beemployed to mimic the mechanical activation of the knee actuator 300, bysimply measuring the angle of flexion of the ankle and unlocking theknee actuator 300 at a predetermined angle, a more advanced controlprogram is a rule-based detection algorithm for the cycle-to-cycleselection of the knee actuator 300 setting based on a more comprehensivesampling of kinematic data of the orthotic frame 100.

Input signals form the sensors are periodically sampled as inputs to thecontrol program. The control program may consider the knee angle, theankle angle, the angular velocity of the shank (lower frame 120), thecurrent status of the knee actuator 300 (locked or unlocked), as well asother information.

Data collected from the sensors may be interpreted to identifytransitions between various, discrete, ambulatory activities or states.Referring to FIG. 10, such transitions include transition from standingstable to walking, and from walking to standing stable. Othertransitions include sitting to standing stable and standing stable tositting, and commencing or ending walking uphill, downhill, up steps, ordown steps. Additionally, the sensor data may be interpreted to detectgait events such as initial contact of the foot (heel strike), full footcontact (mid-stance), lifting of the heel, and toe-off.

Data collected during trials of sitting down and standing up activitiesare shown in FIGS. 11A and 11B. Each figure shows measured data from asingle transition (between standing to sitting, and vice versa). Kneejoint angle data gives a direct indication of these transitions.Additionally, foot contacts and structural deformation of the side bargive information that may be used for prediction of the subject'sintention to start the transition. For example, information about loadsgenerated through the frame by muscle activity before motion is achievedmay be predictive of a subject's intention to stand or to sit.

It can be seen with reference to FIG. 11A that, while sitting down froman upright (stable standing) position, certain features can beidentified by observational analysis: 1) torque at the lower bar X-axisincreases (positive torsion moment) when knee flexion starts, and theknee joint velocity increase significantly as is apparent from the slopeof the knee angle curve; 2) knee joint velocity stabilizes approximatelyat 100° of flexion, and X axis torque approximately reaches a neutralvalue; 3) the thigh segment (upper frame 110) begins to acceleratesignificantly (counter clock-wise), and changes its vertical orientationwith respect to ground; and 4) foot contact sensors indicate contact andthen non contact since the subject is trained to sit using his/hernon-orthotic leg.

Similarly, as the subject begins to stand up (referring to FIG. 11B),recognizable features include: 1) a significant increase in X-axisdeformation (torsion moment), at the lower bar of the orthosis, followedby a decrease, appears when the subject initiates the transition andbefore other motion information indicates this (so that, as with thestanding to sitting transition described above, loading informationgives advanced information about the subject's intent); 2) the kneebegins to extend from a flexion of around 100°; 3) the knee ends at fullextension, coincident with ankle flexion a neutral position, when thesubject is standing stable; 4) the thigh segment (upper frame 110)begins to accelerate significantly (clock-wise) and changes itshorizontal orientation with respect to the ground; and 5) given that thecorrect starting position supposes that ankle is in dorsiflexion, whileputting weight on the rear part of the foot contact sensors at the heelwould be pressed.

Accordingly, it can be recognized that processing and analysis of thesensor data can result in accurate recognition of activities performedby a patient wearing the IKAFO 10, based on rules derived from themeasured and expected sensor data during transition from one activity(or state) to another.

In addition to the activities of sitting down and standing up, otheractivities of interest include initiating and stopping walking, andtransitions to and from walking upslope and downslope, and transitionsto and from walking up and down steps.

Data collected during trials of start walking and stop walkingactivities are shown in FIGS. 12A and 12B. In starting walking (gaitinitiation) from stable standing (referring to FIG. 12A), a negativestrain related to torsion moment at the lower frame 120, is measuredbefore joints motion begins, and can give “predictive” information ofsubject's intention to initiate gait. Heel off occurs at the start ofgait initiation, and is indicated by foot contact sensors 870 indicatingno contact by the rear of the foot, and contact by the front of thefoot. Ankle dorsiflexion begins at heel-off.

The foot begins to accelerate faster than other segments. Knee flexionstarts after ankle dorsiflexion.

As the heel rises, the foot segment tilts with respect to ground. Theshank and thigh (lower and upper frames 110, 120) both tiltsignificantly indicating the beginning of the transition.

In stopping walking (transitioning from walking to stable standing)(referring to FIG. 12B), the knee angle stabilizes at full extensionwhile decelerating. The ankle joint reaches a neutral position from adorsiflexion trajectory.

The knee is held at full extension during a short transient, while theankle is still in plantar flexion. A delayed heel strike event isdetected in comparison with a continued gait pattern. Torsion momenttrends to stabilize to a static situation.

Data collected during trials of going up and down stairs are shown areshown in FIGS. 13A and 13B, respectively. Signals from sensors weremeasured during negotiating three stair steps up and down. The kneejoint was locked during these activities.

While negotiating stairs, ankle joint angle and strains recorded at thex-axis of the side bar 112 of the lower frame 120 give the most valuableinformation among the data shown in the figures. While knee joint islocked during these activities, tilt information of the upper and lowerframes 110, 120 is not primal, but foot segment tilt as related withankle joint relative angle and velocity provides information about theprogression of this activities. Foot contact sensor activation is quitevariable and dependant on the way the subject deals with each tread, sothis information is considered as supporting but not essential for thisdetection.

Data collected during trials of walking up and down a slope are shownare shown in FIGS. 14A and 14B, respectively.

Ankle joint angle data discriminates clearly between both transitions(level to up slope and level to down slope). Also, deformation along theperpendicular axis of the side bar 112 of the lower frame 120 featureshigh peaks distinguishable from those present during level walking.Correlation of the side bar deformation and the ankle angle provides alot of knowledge about the upslope and downslope activities. Footcontact sensor information is not reliable during up and down slopewalking due to drastic changes in the way the subject applies foot loadover the sloped surface.

The activities and transitions are generally considered to each beginand end in the stable standing state. Accordingly, it is desirable forthe stable standing state to be well defined by the available signals.The static, stable standing state may be features such static conditions(no angular velocities or accelerations of the upper and lower frames110, 120 and ankle and knee joints 140, 200). The knee is generallyfully extended, and the ankle joint at a neutral position (within a+/−5° range). The upper and lower frames 110, 120 are in a verticalposition, and the foot support is in a horizontal position. The heel andtoe both contact the ground, and mean pressure at fore and rear footzones trends to stabilize.

In addition to recognition of activities performed by a patient wearingthe IKAFO 10, gait events (or particular phases of the gait cycle) maybe similarly determined by analysis of the sensor data. Referring toFIG. 15A, joint angles, foot contacts (rear and front), and torque ofthe lower frame 120 are shown for a normal gait during four gait cycles.The following gait cycle transitions or events are apparent.

Foot flat to heel off: Pressures sensors at the rear of the foot are notpressed, the knee joint is at generally fully extended, and dorsiflexionof the ankle increases.

Heel off to Swing: Foot contact sensors at both the front and rear ofthe foot indicate no contact after toe off, foot rotation transitionsfrom positive to negative, knee joint angular velocity (apparent fromthe slope of the knee angle curve) increases and the ankle continues aplantar flexion trajectory.

Swing to Heel strike: Foot contact sensors at the rear of the foot arenot pressed, the knee joint is at full extension while ankle joint isalmost at neutral position, and angular velocity of the shank (lowerframe 120) features negative peaks at relative high frequencies.

Heel strike to Foot flat: Foot contact sensors at both front and rearparts of the foot indicate contact, ankle dorsiflexion increases, and,during complete stance, foot velocity is approximately zero.

It can therefore be recognized that important gait cycle transitions orevents are recognizable by analysis of various sensor data and that eachof the above gait cycle transitions or events may be associated withdistinct features of more than a single sensor or sensor type.

While FIG. 15A shows sensor data measured during a normal gait, apatient wearing the IKAFO often will have some form of gait abnormality.Accordingly, recognition of gait cycle transitions or events accordingto more than a single criterion is important FIG. 15B shows datacollected by a subject simulating an abnormal gait of a pathologicalsituation by walking with the forefoot continuously in contact with theground as if being unable to raise the foot for initial swing.

A logical consequence of the simulated abnormal gait is the alteredshape of the swing phase angles of both the knee and ankle. Contactinformation of the heel is shifted remarkably, and forefoot contactinformation is not reliable during nearly the entire task. Use ofredundant information from the various, different sensors helps toconfirm gait cycle transitions and events despite potential deviationsof any single measurement from a normal or ideal gait.

Based on observed correlations between activity transitions, as well asvarious activity or gait phases, rules can be defined for recognition ofthe activities and activity or gait phases. These rules may beimplemented in the control program of the ambulatory unit to providereal-time evaluation of the sensor data and recognition of activitiesand activity or gait phases, in support of the control program ingeneration of control signals for actuators of the IKAFO.

Additionally, such rules may be implemented in a diagnostic program thatis executed in the base unit, to provide information regarding apatient's usage of the IKAFO. The diagnostic program may provide adetailed usage profile, as well as analysis of the patient's measuredgait, which is useful for fitting or adjusting the IKAFO to a patient'sneeds as well as determining therapeutic progress or success in thepatient's treatment.

An example rule set is described, based on sensor data according toTable 1 below. As noted above, certain mechanical and kinematic aspectsof the orthotic frame may be measured by more that a single sensor orsensor type, and therefore multiple different rules may be devised foreach activity and activity or gait phase. Also, as noted above,variations or abnormalities of a patients individual gait pattern mayresult in modification to rules expressed, or in entirely differentrules than those described herein. Accordingly, the rule set describedherein is an example only, and is not intended as an expression of allpossible or all desirable rules that may be implemented by the controlprogram or the diagnostic program.

The rules described are based generally on instantaneous information incomparison with signal thresholds, identified in Table 2 for the sensordata set of Table 1. The signal threshold values may be derived fromobservational analysis of measured mechanical and kinematic sensor data.

TABLE 1 fcs_fore Foot contact sensor (forefoot) fcs_rear Foot contactsensor (heel) KA Knee Angle KV Knee Angular Velocity. Kv_sign Sign (‘+’= 1 or ‘−’ = 0) of knee angular velocity. AA Ankle Angle. AV Ankleangular Velocity. d1 Torsional deformation of the side bar of the lowerframe 120 (X axis) Ddef d1 derivative

TABLE 2 thr_ka Threshold for knee angle signal. thr_ka2 Second thresholdfor knee angle signal. thr_aa Threshold for ankle angle signal. thr_aa_m‘Medium’ Threshold for ankle angle signal. thr_aa_l ‘Low’ Threshold forankle angle signal. thr_kv Threshold for knee angular velocity. thr_avThreshold for ankle angular velocity. thr_fcs_rear Threshold for footcontact sensors. A thr_fcs_fore value below the threshold indicatesfloor contact. thr_d Threshold for structure deformation signal.thr_ddef Threshold for differential of structure deformation signal.

Rules for detecting transition between standing stable and walking, andbetween walking and standing stable, are shown in Tables 3 and 4,respectively. Data samples are indicated for a given sample interval (k)or a previous sample interval (k−1). Signal redundancies are indicatedby consecutive table rows that are not separated by “&”, whereinmultiple sensors provide the same or similar information. The firstcolumn indicates the sampled signal, while the second column indicatesthe associated sensor.

TABLE 3 fce_rear(k − 1) < thr_fce_rear & Rear foot contact sensorfcs_rear (k) > thr_fcs_rear abs(d(k)) < thr_d & Strain gaugesabs(AA(k)) > thr_aa KA(k) > thr_ka2 Knee angle sensor

TABLE 4 (KA(k) < thr_ka2) Knee angle sensor & abs(AV(k)) < thr_av Ankleangle sensor & abs(AA(k)) < thr_aa Ankle angle sensor & abs(ddef(k)) <thr_ddef strain gauges

Thresholds are derived to obtain detection referenced to contactinformation from the foot contact switches and supported by redundancyintroduced with kinematics and supported forces of the orthotic frame.Extracted parameters such as differential of measured strain and angularvelocity calculated by derivation of joint angular information are usedin the illustrated rule. Also, alternative sensors may be employed suchas inertial measurement units 860 may provide knee or ankle angle orangular velocity information in addition to, or instead of, the knee andankle angle sensors. A high reliability of detection can be concludedfrom the results after a proper tuning procedure of the state machineparameters, as illustrated in FIG. 16A.

In order to discriminate between stance and swing phases during normalwalking, rules such as those described in Tables 5-8 are be defined.Gait initiation recognition is assumed, and the definition of an initialstate is required to differentiate between standing stable conditionsand starting walking (a brief start state). Table 5 illustrates a rulefor detecting the transition from start to stance.

TABLE 5 fcs_rear(k) < thr_fcs_rear Rear foot sensor fcs_fore(k) <thr_fcs_fore Forward foot sensor & KA(k) < thr_ka Knee angle sensor

Table 6 summarizes a rule to detect the transition between stance andswing phases of a normal gait.

TABLE 6 fcs_fore(k) > thr_fcs_fore Forward foot contact sensorabs(KV(k)) > thr_kv Knee angular velocity AA(k) > thr_aa & Knee anglesensor, KA(k) < thr_ka & Ankle angle sensor abs(AV(k)) < thr_av &fcs_rear(k) > thr_fcs_rear Rear foot contact sensor & fcs_rear(k − 1) <thr_fcs_rear Rear foot contact sensor

As discusses above, while evaluation of a normal walking gait provides auseful baseline for analysis and for generation of rules for detectinggait activities and events, pathological conditions resulting in anabnormal gait must be considered Table 7 illustrates another rule fordetecting transition between stance and swing phases, but in a simulateddrop foot gait.

TABLE 7 fcs_fore(k) > thr_fcs_fore Forward foot contact sensorabs(KV(k)) > thr_kv Knee angle sensor AA(k) > thr_aa & Knee anglesensor, KA(k) < thr_kv & Ankle angle sensor abs(AV(k)) < thr_av &fcs_rear(k − 1) < thr_fcs_rear & Rear foot contact sensor, KV(k) >thr_kv Knee angle sensor fcs_rear(k) > thr_fcs_rear Rear foot contactsensor

Table 8 shows another rule for a simulated drop foot gait, this time fordetecting transition from swing to stance.

TABLE 8 fcs_rear(k) < thr_fsr_rear Rear foot contact sensor kv_sign == 0(−) Knee angle sensor & KA(k) < thr_ka Knee angle sensor & KV(k) <thr_kv Knee angle sensor & fcs_fore(k) > thr_fsr_fore Forward footcontact sensor

Because information extracted from foot contact sensors may beunreliable during a pathological gait situation, a higher level ofredundancy may be introduced to ensure a proper detection of swing andstance phases. FIG. 16B shows a result of recognition of stance andswing phases, with a high reliability, during simulated pathologicalgait case. The reliability of the rules is improved in such an abnormalgait by defining rules that are more independent from the foot contactsensor information that may be lost or unreliable.

For certain transitions, it is useful to consider a single transition asa sequence of partial transition events. For example, Tables 9-11 showrules for detecting a transition from sitting down to standing stable,wherein the transition is considered in three phases Table 9 illustratesa rule for detecting a sitting to a start standing activity, while table10 illustrates a rule for detecting a start standing to a standing upactivity, and table 11 illustrates a rule for detecting a standing up toa standing stable activity. Thus, the transition from sitting down tostanding stable may be viewed as a sequence of activities transitioningfrom sitting to starting to stand, to standing up and finally tostanding stable.

TABLE 9 d1(k) > um_d1 Strain gauge & fcs_rear(k) > fcs_rear Rear footcontact sensor & abs(KV(k)) < um_kv Knee angle sensor & KA(k) > um_kaKnee angle sensor

TABLE 10 AA(k) > um_aa Ankle angle sensor & KA(k) < um_ka Ankle anglesensor & fcs_rear(k) < fcs_rear Rear foot contact sensor KA(k) < um_kaKnee angle sensor

TABLE 11 d1(k) < um_d1 Strain gauge & KA(k) > um_ka Knee angle sensor

Starting from a static seated condition (sitting down), a loading phaseis detected, which indicates the subject's intention to get up, shortlybefore kinematics detect the initiation of the procedure. The transitionends with the subject standing stable.

Similarly, the transition from standing stable to sitting down may beconsidered in a first transition from standing stable to seating(beginning to sit down) and a second transition from seating to thefinal state of sitting down. Tables 12 and 13 illustrate rules for thetransitions from standing stable to seating, and from seating to sittingdown, respectively.

TABLE 12 (d1(k) > um_d1) & Strain gauge, ((abs(KV(k)) > um_kv) Kneeangle sensor abs(KV(k)) < um_kv Knee angle sensor & KA(k) > um_ka Kneeangle sensor

TABLE 13 AA(k) > um_ka Ankle angle sensor & KA(k) < um_ka Knee anglesensor

Starting from a static condition while standing stable, the seatingprocedure is detected based upon cinematic information as can be seenfrom the rule described in tables 12 and 13. In this case, bar loadingdata does not provide much information to detect the subjectinformation. The transition ends with the subject sitting down.

A rule for detecting an activity of climbing stairs (transitioning fromstable standing to going up stairs) is shown in Table 14. The activityis begun from a stable standing state, and the subject initiates theactivity with the non-orthotic leg.

TABLE 14 d1(k) > um_d1 Strain gauge & AA(k) < um_a Ankle angle sensor &fcs_rear(k) == 0 Rear foot contact sensor

Foot contact sensors considered together with strain gauges and anklekinematics provided an efficient and reliable determination of thisactivity. Table 15 illustrates a rule for detecting transition fromclimbing stairs back to stable standing.

TABLE 15 d1(k) > um_d1_min Strain gauge & d1(k) < um_d1_max Strain gauge& (AA(k) < um_a_min) & Ankle angle sensor ((AA(k) > um_a_max)

With the knee joint locked throughout the stair climbing activity,detection based on ankle kinematics is confirmed by load stabilizationaccording to the strain gauge.

Rules for detecting a downslope walking activity are described in Tables16 and 17, wherein the transition from standing stable to downslopewalking is considered in a first transition from standing stable tobeginning downslope, and a second transition from beginning downslope towalking downslope.

TABLE 16 d1(k) < um_d1_min Strain gauge & abs(AV(k) < um_av Ankle anglesensor & AA(k) < um_a_min Ankle angle sensor

TABLE 17 (AV(k) > um_av) & Ankle angle sensor (AA(k) > um_a_dors) d1(k)< um_d1 Ankle angle sensor

The subject begins the transition with the non-orthotic leg, and theorthotic knee joint remains locked during the course of downslopewalking. Heel strike may be significantly delayed during downslopewalking (or during the transition from stable standing to downslopewalking) and so ankle angular information is employed for detection.Also, the strain gauge signal decreases, since weight is shifted to thenon-orthotic leg, and therefore becomes useful to differentiate betweenthis transition and the transition from stable standing to level walking(the start walking activity).

Similarly, a rule for detection of the termination of downslope walking(transitioning from downslope walking to standing stable) employsinformation from the strain gauge and the ankle angle, as seen in Table18.

TABLE 18 (d1(k) > um_d1_min) & Strain gauge (d1(k) < um_d1_max) &(AA(k) > um_a_min) & Ankle angle sensor (AA(k) < um_a_max)

Thus, analysis of the sensor data collected by the ambulatory unit 900may be analyzed, either by the control program of the ambulatory unit900 or by the diagnostic program of the base unit.

In the ambulatory unit 900, information about the ambulatory activities,activity transitions, and activity or gait phases may be used to controlactuators of the orthotic frame 100 to affect active assistivestrategies to assist a patient's gait. For example, activation of theknee actuator 300 to select the stiff mode or the flexible mode may besynchronized to detection of certain gait events.

Also, knowledge of an activity being performed by a patient may be usedto alter such a control function from a baseline. In the event ofupslope or downslope walking, timing between a given gait event andactuation of the knee actuator 300 may be affected for optimalassistance to the patient.

Accordingly, while activation of the knee actuator 300 may be triggeredby detection of a gait event, knowledge of the ambulatory activity thatthe patient is performing allows selection of a gait event mostappropriate for the activity, as well as introduction or modification ofa time delay factor between detection of the gait event and actuation ofthe knee actuator 300, or even modification of threshold levels used forgait event detection during the course of a given activity.

It will be understood that the above-described embodiments of theinvention are illustrative in nature, and that modifications thereof mayoccur to those skilled in the art. Accordingly, this invention is not tobe regarded as limited to the embodiments disclosed herein, but is to belimited only as defined in the appended claims.

1. An actuator having a variable compressive stiffness for placement onan orthosis having a joint portion and arranged for biomechanicalfunctional compensation of ambulatory disorders, comprising: a firstcylinder; a second cylinder slidably disposed at least partially withinthe first cylinder and biased toward an extended position by a firstbiasing member; a shaft slidably disposed at least partially within thesecond cylinder and biased toward an extended position by a secondbiasing member; and a locking mechanism movable between a lockedposition wherein the first and second cylinders are locked together in afixed position, and an unlocked position wherein the first and secondcylinders are movable relative to one another; wherein the actuator isplaced at a joint portion located on the orthosis.
 2. The actuatoraccording to claim 1, wherein the second biasing member provides adifferent biasing force than the first biasing member.
 3. The actuatoraccording to claim 1, wherein the first and second biasing members arecomprised of a first and a second spring, respectively, and the secondspring has a different stiffness than the first spring.
 4. The actuatoraccording to claim 1, wherein the locking mechanism is biased toward thelocked position.
 5. An orthosis for biomechanical evaluation andfunctional compensation of ambulatory disorders, comprising: an orthoticframe having a proximal frame, a distal frame, a foot support, a kneejoint coupling a distal end of the proximal frame to a proximal end ofthe distal frame; a knee actuator disposed on the orthotic frame andconfigured to control flexion of the knee joint according to a variableresistance; a selector having at least a first position wherein the kneeactuator provides a first resistance and a second position wherein theknee actuator provides a second resistance; and a control elementconnected to the selector and configured to move the selector betweenthe first and second position according to at least one aspect of anambulatory or related activity.
 6. The orthosis according to claim 5,wherein the knee actuator comprises a first biasing member for providingthe first resistance and a second biasing member for providing thesecond resistance.
 7. The orthosis according to claim 6, wherein thefirst biasing member is a first spring having a first stiffness.
 8. Theorthosis according to claim 6, wherein the second biasing member is asecond spring having a second stiffness.
 9. The orthosis according toclaim 5, wherein the knee actuator comprises: a first cylinder; a secondcylinder slidably disposed at least partially within the first cylinderand biased toward an extended position by a first biasing member; and ashaft slidably disposed at least partially within the second cylinderand biased toward an extended position by a second biasing member. 10.The orthosis according to claim 9, further comprising a lockingmechanism configured and arranged to selectively lock the first andsecond cylinders together in a fixed position.
 11. The orthosisaccording to claim 9, wherein the second biasing member provides agreater biasing force than the first biasing member.
 12. The orthosisaccording to claim 9, wherein the first and second biasing members arecomprised of first and second springs, respectively, the second springhaving a greater stiffness than the first spring.
 13. The orthosisaccording to claim 5, wherein the knee joint has a variableinstantaneous axis of rotation mimicking an instantaneous helical axisof a human knee.
 14. The orthosis according to claim 5, wherein thecontrol element comprises a mechanical coupling connected between anankle joint connected to the distal end of the distal frame, and theselector, the mechanical coupling being configured to move the selectorbetween the first and second positions according to an angle of flexionof the ankle joint.
 15. The orthosis according to claim 14, wherein thecontrol element is a cable movable according to an angle of the ankle,the cable operating the selector to unlock the knee actuator.
 16. Anorthosis for biomechanical evaluation and functional compensation ofambulatory disorders, comprising: an orthotic frame having a proximalframe adapted for fitting to a user's upper leg, a distal frame adaptedfor fitting to the user's lower leg, a foot support, a knee jointcoupling a distal end of said proximal frame to a proximal end of saiddistal frame, and an ankle joint coupling a distal end of said distalframe to said foot support; a knee actuator disposed on the orthoticframe and configured to control flexion of the knee joint according to avariable resistance; an ankle actuator coupled between said distal frameand said foot support providing a dorsal bias to position said footsupport against dorsal flexion and a plantar bias to position said footsupport against plantar flexion, whereby the ankle actuator controlsflexion of said ankle joint; and a control element connected to the kneeactuator and at least one of the ankle joint and foot support, thecontrol element movable according to an angle of one of the ankle jointand the foot support, the control element arranged to activate the kneeactuator when the ankle joint or the foot support reaches apredetermined degree of flexion.
 17. The orthosis according to claim 16,wherein the control element is a cable movable according to an angle ofthe ankle, the cable operating the selector to unlock the knee actuator.18. The orthosis according to claim 16, wherein said knee actuatorcomprises: a first cylinder; a second cylinder slidably disposed atleast partially within said first cylinder and biased toward an extendedposition by a fast biasing member; and a shaft slidably disposed atleast partially within said second cylinder and biased toward anextended position by a second biasing member.
 19. The orthosis accordingto claim 18, further comprising a locking mechanism configured andarranged to selectively lock said first and second cylinders together ina fixed position.
 20. The orthosis according to claim 18, wherein saidsecond biasing member provides a greater biasing force than said firstbiasing member.